One of the barriers to HIV eradication is viral latency. For example, widely used highly active antiretroviral therapy (HAART) is only effective in reducing virus load in the blood and slow down the development of AIDS, but cannot completely eradicate HIV from an infected individual. Viral reservoirs established early during the infection remain unaffected by the anti-retroviral therapy for a long time and are able to reinitiate systemic infection upon interruption of the treatment. Therapeutic targeting of viral latency will require a better understanding of the basic mechanisms underlying the establishment and long-term maintenance of HIV in resting memory CD4 T cells, the most prominent reservoir of transcriptionally silent provirus.